Vibratory molding process and product

ABSTRACT

A fastener strip is disclosed having a permanently sealed, airtight portion and a reclosable portion capable of maintaining an airtight seal when closed. The permanently sealed portion is generally planar and essentially impervious to air flow. The reclosable portion includes a ridge and a trough joined at their adjacent ends to a plug, which prevents air from leaking from the adjacent end of the reclosable portion. Additionally, a dam joins the plug to the first backing in an essentially airtight seal, and joins the plug to the second backing in an essentially airtight seal. A method and apparatus for sealing portions of a thermoplastic fastener strip are also disclosed. A method is additionally disclosed for vibrating and molding thermoplastic materials in which a flow of malleable thermoplastic material is initiated and molded with an effectively dimensioned vibrator that is unitary with a first matrix for guiding and molding the malleable polymer.

FIELD OF THE INVENTION

[0001] The invention relates generally to a process for permanentlysealing portions of reclosable fastener strips that includes the use ofa vibrating horn to heat and mold the fastener strip. The invention alsorelates generally to an apparatus for permanently sealing portions ofreclosable fastener strips and to reclosable fastener strips thatinclude permanently sealed airtight portions.

BACKGROUND OF THE INVENTION

[0002] Reclosable fastener strips are widely used in the packagingindustry as components for reclosable plastic bags, among other things.Typically, the fastener strips are manufactured in long, continuouslengths that are wound on reels or accordion-folded in boxes for storageand shipping.

[0003] These continuous lengths are usually subsequently cut to a sizesuitable for attaching to individual bags on, for example, a form andfill machine. The fastener strips are normally composed of thermoplasticmaterials, such as polyethylene, polypropylene, ethylene vinyl acetate,polyethylene terephthalate, polyvinylidene fluoride, acrylonitrilebutadiene styrene or the like. For example, the fastener strips ofteninclude backings comprised of a polyethylene-ethylene vinyl acetateblend. The backings often include a profile portion having ridges andtrough composed of polyethylene terephthalate. A representative fastenerstrip of the prior art is depicted in FIGS. 17-19.

[0004] In order for the cut end of the fastener strip to seal againstair leakage in or out of the reclosable bag, the end must be closed offin some manner. Also, the closed-off portion should be thinned andflattened to facilitate the cutting operation. Adhesives and thermalwelds, notably “spot seals,” have been utilized in the past. However,neither of these techniques is entirely reliable, and both of thesetechniques tend to deform or obstruct portions of the fastener stripsthat are intended to remain unaffected and, therefore, reclosable.

[0005] Vibratory welding processes, including sonic and ultrasonicprocesses also have been used in the manufacture of reclosablethermoplastic plastic bags, as well as other thermoplastic work piecesusing known power supplies, transducers, boosters, and harmonicallybalanced horns. Conventional horns used in these processes are ofseveral different types. These types include flat horns, knurled horns,and reversed knurled horns. However, each one of these horns has twomajor drawbacks. One drawback is that these horns typically imprint anundesirable contour on vibrated regions of the thermoplastic work piece.The other drawback is these horns often deform nearby unvibratedportions of the thermoplastic work piece. For example, previouslydisclosed horns typically deform thermoplastic fastener strips inreclosable portions that adjoin the vibrated region. This deformationcreates gaps that prevent the fastener strips from forming an airtightseal.

[0006] Ultrasonic processes are also employed to reduce the thickness ofthermoplastic fastener strips to facilitate cutting and sealing thethermoplastic fastener strips and associated bags. These previouslydisclosed processes cannot be relied upon to create an airtight seal,because the prior art ultrasonic horns typically a) imprint anundesirable contour on vibrated regions of the bag so as to createleaks, and b) deform nearby unvibrated portions of the thermoplasticwork piece.

[0007] Therefore, a need exists for a new process for permanentlysealing portions of reclosable thermoplastic fastener strips. Desirably,the new process provides an airtight seal in both the vibrated andunvibrated portions of the fastener strip.

SUMMARY OF THE INVENTION

[0008] The present invention provides a fastener strip having apermanently sealed, airtight portion and a reclosable portion capable ofmaintaining an airtight seal when closed. The permanently sealed portionis generally planar and essentially impervious to air flow. Thereclosable portion includes a ridge and a trough joined at theiradjacent ends to a plug, which prevents air from leaking from theadjacent end of the reclosable portion. Additionally, a dam joins theplug to a first backing in an essentially airtight seal, and joins theplug to a second backing in an essentially airtight seal.

[0009] The invention also provides a method for sealing portions of athermoplastic fastener strip. The method includes vibrating a portion ofa conventional, thermoplastic fastener strip, which is capable ofmaintaining an airtight seal, so as to produce a malleable portion. Afirst matrix is pressed against the malleable portion to produce a firstshape, and a second matrix is pressed against the malleable portion toproduce a second shape for permanently sealing a portion of the fastenerstrip. Preferably, a dual-purpose vibrator/matrix is utilized to vibratethe fastener strip and produce the first shape. In addition, the firstand second shapes are also enhanced by other matrices at separatestages.

[0010] Pressing the malleable portion to produce the first shape mayinclude flattening the malleable portion and displacing at least some ofthe malleable portion to produce an essentially airtight plug. The plugjoins the planar portion in an essentially airtight seal and joins theadjacent end of the reclosable portion in an essentially airtight seal.

[0011] Pressing the malleable portion to produce the second shape mayinclude further flattening the malleable portion and displacing at leastsome of the malleable portion to produce an essentially airtight dam.The dam joins the plug to a first backing of the reclosable portion inan airtight seal and, also, joins the plug to a second backing of thereclosable portion.

[0012] The invention also provides an apparatus for sealing portions ofa fastener strip. The apparatus includes a vibrator for vibrating aportion of the fastener strip so as to increase the malleability of theportion, a first matrix constructed and arranged for pressing againstthe malleable portion to produce a first shape for sealing the fastener;and a second matrix constructed and arranged for pressing against themalleable portion to produce a second shape for sealing the fastener.

[0013] In a broader aspect, the invention is an ultrasonic polymerforming process for thermoplastic materials in which the improvementincludes guiding the flow of malleable polymer to a predeterminedlocation with an effectively dimensioned vibrator that is unitary with afirst matrix for guiding and molding the malleable polymer. For example,the predetermined location may be a location in which additional polymeris desired to render the area stronger or more aesthetically pleasing,or to fill any gaps.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a truncated perspective view of a fastener strip of thepresent invention;

[0015]FIG. 2 is an elevation view of the fastener strip depicted in FIG.1;

[0016]FIG. 3 is a cross-section taken along line 3-3 of FIG. 2;

[0017]FIG. 4 is a cross-section taken along line 4-4 of FIG. 2;

[0018]FIG. 5 is a cross-section taken along line 5-5 of FIG. 2;

[0019]FIG. 6 is a perspective view of a first stage of an apparatus ofthe present invention;

[0020]FIG. 7 is a perspective view of a vibrator of the presentinvention;

[0021]FIG. 8 is an end view of the vibrator depicted in FIG. 7;

[0022]FIG. 9 is a partial cross-section of the vibrator taken along line9-9 of FIG. 8;

[0023]FIG. 10 is an elevation of the first shape, which is produced bythe first stage;

[0024]FIG. 11 is a perspective view of a second stage, a third stage, afourth stage and a fifth stage of the apparatus depicted in FIG. 6;

[0025]FIG. 12 is a perspective view of a die for the second stage of thepresent invention;

[0026]FIG. 13 is an elevation of a second shape, which is produced bythe second stage;

[0027]FIG. 14 is a perspective view of a die for the third stage of thepresent invention;

[0028]FIG. 15 is a perspective view of a die for the fourth stage of thepresent invention;

[0029]FIG. 16 is a perspective view of a tensioner of the presentinvention;

[0030]FIG. 17 is a plan view of a prior art fastener strip, includingtwo backings;

[0031]FIG. 18 is an elevation view of one of the prior art backingsdepicted in FIG. 15; and

[0032]FIG. 19 is an elevation view of the other of the prior artbackings depicted in FIG. 15.

DETAILED DESCRIPTION OF THE INVENTION

[0033] In a preferred embodiment, the invention includes a fastenerstrip such as fastener strip 100 depicted in FIG. 1. Fastener strip 100includes at least one reclosable portion 120 and at least onepermanently sealed, generally planar portion 140. Although theperspective view shown in FIG. 1 is necessarily truncated, due to spacelimitations, it is contemplated that fastener strip 100 may be wound ona reel or accordion-folded in a box for convenient shipping and storageand include hundreds or even thousands of reclosable portions 120 andgenerally planar portions 140.

[0034] Reclosable portion 120 includes first backing 122 and troughs124, which typically extends lengthwise along fastener strip 100.Reclosable portion 120 also includes second backing 126 and ridges 128for mating with troughs 124 in an airtight, reclosable seal thatessentially prevents air flow from one side of the seal to the other.Flap or flange 127 conveniently extends from second back 122 to anexterior side of fastener 100 in order to protect trough 124 and ridge128 from damage and to facilitate a user's grip for opening fastenerstrip 100.

[0035] The relative positions of troughs 124 and ridges 128 are depictedin FIG. 1 are arbitrary and need not be as shown for the invention tosucceed. Also, either first backing 122 or second backing 126 may bepositioned on the exterior side of fastener strip 100 and either of thebackings 122, 124 may extend in the form of a flange, such as flange127. The thicknesses of backings 122, 124 are often in the range ofabout 10 to 20 thousandths of an inch and the heights of trough 124 andridge 128 are often in the range of about 50 to 100 thousandths of aninch. The invention however is not limited to these ranges.

[0036] Commonly, the thickness of planar portion 140 is about thethickness of one of the backings 122, 124 to about the combinedthickness of both of the backings. Planar portion 140 is essentiallyfree of mating ridges and troughs, such as trough 124 and ridge 128, andincludes essentially no void spaces.

[0037] Plug 160 joins troughs 124 and ridges 128 in an airtight seal atadjacent end 130 of reclosable portion 120. Troughs 124 and ridges 128define longitudinal interstitial voids (best seen in FIG. 3) thatcommunicate hydraulically lengthwise along reclosable portion 120. Evenif troughs 124 and ridges 128 mate effectively so as to prevent air flowbetween them from one side of fastener 100 to the other (for example,from the interior side of fastener strip 100 to the exterior of fastenerstrip 100), the ends of trough 124 and ridge 128 must be sealed toprevent air from flowing longitudinally through these voids and passingthrough end 130. Plug 160 provides this seal.

[0038] Dam 180 joins plug 160 to first backing 122 and to second backing126 as depicted in FIG. 1. Dam 180 is essentially impervious to air flowand forms airtight seals where it meets plug 160, first backing 122 andsecond backing 126, respectively. A primary purpose of dam 160 is toprevent air one side of fastener strip 100 from leaking around plug 160to the other side of fastener 100.

[0039] The relationship of plug 160 to dam 180 is best seen in FIG. 2.FIG. 2 shows how plug 160 seals end 130 of reclosable portion 120 toprevent longitudinal interstitial voids from passing air through end130. Dam 180 joins and seals the backings 122, 126 with plug 160 andplanar portion 140. Lines 3-3, 4-4 and 5-5 correspond to cross-sectionsdepicted in FIGS. 3-5.

[0040] Inspection of FIGS. 1-3 indicate that line 3-3 of FIG. 2 is at ornear end 130. As can be seen in FIG. 3, trough 124 and ridge 128 defineinterstitial voids that are sealed by plug 160. The view in FIG. 3 looksaway from planar portion 140 and toward reclosable portion 120.Longitudinal interstitial voids can be seen in cross-section, with plug160 filling the voids. Significantly, FIG. 3 shows that trough 124 andridge 128 are not significantly deformed at line 3-3 and, therefore, arecapable of creating an airtight, reclosable seal across fastener strip100. FIG. 3 is representative of reclosable portion 120, except thatplug 160 covers over and/or infiltrates the interstitial voids.

[0041] The view in FIG. 4 is in the same direction as that of FIG. 3,but from a position closer to planar portion 140. Only vestiges oftrough 124 and ridge 128 are apparent, and these are essentially filledby plug 160. FIG. 4 is representative of plug 160, except that thevestiges are present.

[0042]FIG. 5 shows a relatively flattened and homogeneous cross-section,as compared to FIGS. 3 and 4. No vestiges of trough 124 and ridge 128are visible. FIG. 5 represents the juncture of dam 180 with planarportion 140.

[0043] Turning now to FIGS. 17-19, prior art fastener strip 10 includesfirst backing 22, having a plurality of longitudinal troughs 24 thereon,and second backing 126, which has a plurality of longitudinal ridges 28and flap or flange 27. At least one of the troughs 24 reclosably mateswith one of the ridges 28 to produce an essentially airtight seal thatprevents air leakage between interior and the exterior sides of fastenerstrip 10.

[0044] Longitudinal interstitial voids commonly exist between trough 24and ridge 28. While the voids do not necessarily interfere with theairtight seal between the sides of fastener strip 10, the voids permitair flow longitudinally along trough 24 and ridge 28. Fastener strip 10is composed of a material that becomes progressively more fluid withincreasing temperature, hereinafter referred to as a “thermoplastic”material.

[0045]FIG. 6 depicts first stage 256 of apparatus 200 of the presentinvention for sealing portions of a prior art fastener strip, such asthermoplastic fastener strip 10 shown in FIGS. 17-19. First stage 256 ofapparatus 200 includes vibrator 220 for vibrating a portion of fastenerstrip 10 to produce a relatively more malleable portion 212, best seenin FIG. 9. FIG. 6 also shows anvil 230, which supports fastener strip 10from below during the vibrating, and four pneumatic piston and cylinderassemblies 202. The use of four pneumatic pistons 202 assures that theanvil 230 is properly aligned and level, and also helps direct more ofthe energy from vibrator 220 to the fastener strip, rather than causingthe anvil 230 to vibrate. First stage 256 is positioned at location 258,which is a short distance away from stages 276, 296, 316 and 320 (bestseen FIG. 11) of apparatus 200.

[0046] Vibrator 220, illustrated in FIG. 7, includes pneumatic actuator231, ultrasonic horn or resonator 233 and first matrix 240. Actuator 231receives compressed air and provides energy to vibrator 220 in the formof mechanical vibrations in the range of about 10,000 to about 100,000cycles per second, more preferably at least about 20,000 cycles persecond. Horn or resonator 233 focuses and intensifies the vibrations atfirst matrix 240, which is a single, integral unit with horn 233.

[0047] Horn 233 is also known as a solid resonator, a concentrator, or amechanical amplifier. Horn 233 is dimensioned to be resonant at apredetermined frequency of vibration. When horn 233 is energized at itsproximal input surface by an actuator 231, it provides ultrasonic energy(vibrations) at its opposite distal end to a workpiece that is in forcedcontact with the distal end.

[0048] As depicted in FIGS. 7-9, first matrix 240 is the distal end ofhorn 233. Alternatively, first matrix 246 can be constructed as aseparate die and securely mounted on the distal end of horn 233. It isbelieved that fashioning first matrix 240 integrally with horn 23,rather than as a separate die mounted on horn 233, tends to promotesefficient and reproducible transmission of the vibrations. In eithercase, first matrix 240 is located at the distal end of horn 233 and canbe utilized to press and mold a thermoplastic substrate, such asfastener strip 10, while vibrator 220 is vibrating.

[0049] Details of first matrix 240 are presented in FIG. 8. First matrix240 includes a planar face 246 having cutouts 248, 250. Groove 252 ofapproximately semicircular cross-section extends across face 246 fromcutout 248 to cutout 250. FIG. 8 illustrates that groove 252 isgenerally linear along the longitudinal axis of fastener strip 10 andthat cutouts 248, 250 are each generally symmetrical and aligned along ashared axis of symmetry. The groove axis and the cutout axis are offsetand generally parallel to each other. During use, the groove axis isaligned with and positioned directly over trough 24 and ridge 28.

[0050]FIG. 9 is a partial cross-sectional view taken along the grooveaxis of FIG. 8. It is evident from FIG. 9 that horn 233 is unitary withmatrix 240. Cutouts 248 and 250 each include a transition volume 251,253 having a depth that increases as distance from groove 252 increases.Each cutout 248, 250 has an arcuate cross-section, with the arcspositioned convexly to each other.

[0051] During use, first matrix 240 is placed over fastener strip 10,with groove axis 252, trough 24 and ridge 28 generally aligned. Moveableanvil 230 includes a generally planar face 23 that supports fastenerstrip 10 from below. Alternatively, fastener strip 10 may be placedbetween two vibrators 220 (not shown) for vibrating and pressing betweentwo first matrices 240 (not shown).

[0052]FIG. 9 depicts vibrator 220 as it initially impinges on fastener10. At this time, the tension on fastener strip 10 is carefullycontrolled by a conventional tensioner. For example, dancer rollerassembly 216 depicted in FIG. 15 are suitable for tensioning fastenerstrip 10. Additionally, as seen as FIG. 16, fastener 10 has beenpreheated by means of preheaters 217 and 219 to a temperature greaterthan room temperature and less than the melting range or index of thethermoplastic material that composes fastener 10 so as to remove, curl,and facilitate molding. As pneumatic assemblies 202 (best seen in FIG.6) apply calibrated force to elevated anvil 230, the pressure that face246 applies to fastener strip 10 and the distance between face 246 andface 236 are carefully controlled. Preferably, face 246 presses uponfastener strip 10 with a force of from 10 to 500 pounds per square inch,ideally about 70 pounds per square inch. Preferably, face 246 and face236 are not permitted to touch.

[0053] Vibrator 220 vibrates a portion of fastener strip 10 so as togenerate internal friction within fastener strip 10, causing a portion212 of fastener strip to become relatively more malleable. Thetemperature of the vibrated portion often increases during thevibrating. The pressure exerted by first matrix 240 tends to displacesome of the malleable portion in predictable directions. For example,the depth of transition volumes 251, 253 and the depth of groove 252 arecalculated to displace a certain amount of the malleable portion alonggroove 252, and displace a certain amount of the malleable portion to orfrom the transition volumes 251, 253. Malleable material is alsodisplaced transversely from the groove axis as first matrix 240 flattensthe region between cutouts 248, 250.

[0054] First matrix 240 is properly shaped to press and extrude thedisplaced material in desired directions and, also, to mold and retainthe displaced material at desired destinations. Preferably, the materialdisplaced by first matrix 240 forms plug 160 or dam 180 of fastenerstrip 100 of the present invention; most preferably plug 160. The resultis a product having first shape 242, depicted in FIG. 10, whichsignificantly differs from the shape of fastener strip 10.

[0055] Referring now to FIG. 10, first shape 242 includes flattenedportion 142, elongated hump 144 and a curved portion abutting end 130 ofreclosable portion 120. Hump 144 corresponds to the shape of groove 252.The curved portion corresponds to the shape of transition volumes 251,253. First shape 242 facilitates sealing, and is sufficiently similar tothe shape of fastener strip 10 so as to be reproducibly molded byvibrating and pressing in a single stage, as described above.

[0056]FIG. 11 is a perspective view of second stage 276, third stage296, fourth stage 316 and fifth stage 320 of apparatus 200. Each ofthese stages is located a short distance from each other at locations278, 298, 318 and 320, respectively. Each of these stages respectivelyhas a dedicated pneumatic piston and cylinder assembly 261, 281, 301,321 that forces an anvil down upon the fastener strip. Second stage 276,third stage 296, and fourth stage 316 are pressing stages that utilizedies 266, 286, 306 to support the fastener strip from beneath.

[0057] As with first stage 256, the temperature, pressure, time anddistance between die faces 266, 286, 306 and respectively associatedanvils are carefully controlled. The optimum combination of thesefactors depends on the precise nature of the fastener strip and thespecifications of the finished seal portion. However, die temperaturesof about 350 to about 400 degrees F. and pressures of about 60 to about80 pounds per square inch have been employed successfully in pressingstages 276, 296, 316 with a pressing time of about half a second. Fifthstage 320 cools the finished product, which is fastener strip 100. Alsoshown in FIG. 11 is conveyor belt 321 which intermittently advancesfastener strip 100. Conveyor belt 321 is preferably constructed of asilicone blend to resist heat, but also has a surface 323 which sticksto or retains fastener strip 100 when it is heated sufficiently to betacky. The fastener strip when it is heated in malleable-like taffy, butthe tension on conveyor belt 321 and thereof fastener strip 100 iscarefully controlled preferably by a servo motor. As a result, thefastener strip 100 remains in its original size and configuration,except where it is shaped by die faces 266, 286 and 306.

[0058]FIG. 12 shows die 264, which is typically utilized at second stage276. Die 264 includes generally planar face 266 and a pair of oppositelylocated arcuate cutouts 268, 270, which are positioned with their convexsides facing each other. As compared to cutouts 248, 250 of first stage256, cutouts 268, 270 are positioned closer together and have greaterradii. As seen in FIG. 11, silicone coated stripper plate 264A ispositioned between face 266 and fastener strip 100, to facilitateseparation of face 266 from fastener strip 100 after compression.Consequently, only stripper plate 266 of die 260 touches first shape242. Pressing die 264 against first shape 242 causes flattened portion142 and hump 144 to become further flattened. Additionally, die 264displaces material toward adjacent end 130, which ultimately forms dam180. Preferably, plug 160 is not significantly affected by die 264.

[0059] The action of die 264 on first shape 242 produces second shape262, which is depicted in FIG. 13. Flattened portion 146 is thinner, ascompared to hump 144. Preferably, dam 180 is formed primarily bymaterial displaced by die 264 and extends from backings 122 and 126 andpartially surrounds plug 160.

[0060] Overall flatness of the finished fastener strip, such as fastenerstrip 100, is an important requirement for many fastening applications.Third stage 296 works with die 284, as depicted in FIG. 14, to generallyflatten backings 122, 126 of fastener strip 100 and ensure thatreclosable portion 120 and planar portion 140 are coplanar. Face 286defines longitudinal channel 284, which is significantly deeper andwider than groove 252. Accordingly, die 284 has relatively little effecton plug 160 or dam 180. Third stage 296 produces third shape 282, whichis similar to the shape of fastening strip 100. Again, a stripper plate284A is utilized to facilitate separation after compression.

[0061] Die 304 has a generally planar face 306 with cutouts 308, 310 andis similar to die 262, except that cutouts 308, 310 are positionedcloser together and have greater radii than cutouts 268, 270. Whenpressed against third shape 282 under proper conditions of pressure,temperature and spacing, die 304 completes planar portion 140 andproduces fourth shape 302, which is the shape of fastener strip 100.Fifth stage 316 cools fastener strip 100 so that it may be moreconveniently transported and packaged. Again, a stripper plate 304A isutilized to facilitate separation. After the shaping of fastener strip100 is completed, conveyor belt 321 advances the fastener strip to asecond conveyor 101. As it cools, fastener strip 100 no longer adheresto belt 100, so it can be removed without stretching or distortion. Thelack of tension on fastener strip 100 is crucial to maintaining thedimensions and configuration of the fastener strip 100. Fastener strip100 is then advanced by second conveyor 101 to a take up reel 103, againmaintaining minimum tension and compression of the fastener strip 100.

[0062] The invention also provides a method for sealing portions of athermoplastic fastener strip, which process will now be described. Theinvention is not limited to the described process, starting materials,equipment or products.

[0063] A prior art fastener strip, such as fastener strip 10 is thestarting material. A tensioning assembly, such as a dancer rollerassembly 216 depicted in FIG. 16, is suitable for tensioning fastenerstrip 10. Dancer roller assembly 216 applies a precise tension tofastener strip 100, as will be appreciated and understood bypractitioners. Fastener 100 is preheated by preheaters 217 and 219 to atemperature warmer than room temperature and cooler the melting point orindex of the thermoplastic material that composes fastener strip 100.For example, a temperature in the range of about 120° to about 130degrees F. is often useful. Control of temperature and tension preventsdistortion of the fastener strip 100. Fastener strip 100 is thenadvanced by conveyor belt 321.

[0064] A portion of fastener strip 10 is vibrated between a vibrator andan anvil at a first stage. The vibrating is effective to increase themalleability of the portion, as compared to the malleability of fastenerstrip 100 before vibrating. A first matrix is pressed against themalleable portion to produce a first shape. The pressing may be carriedout simultaneously with the vibrating. Second matrix, third and fourthmatrices are subsequently pressed against the malleable portion toproduce a second shape, a third shape and a fourth shape, respectively.Each pressing is accomplished in a separate stage at a differentlocation. The fastener strip may be heated before or during the stages.The finished fastener strip is cooled to room temperature and may thenbe wound on a spindle or roll for later use by the bag converter, againat a precise tension to avoid distortion.

[0065] The vibrator oscillates in contact with the fastener strip at afrequency of about 10,000 to about 100,000 cycles per second, preferablyat least about 20,000 cycles per second. As described above, thevibrator includes an actuator, a resonator or horn, and a first matrix,which is unitary with the horn. The vibrator is positioned over thefastener strip and an anvil is positioned under and in contact with thefastener strip. Preferably, the vibrator does not touch the anvil.Alternatively, two or more vibrators may be brought in to contact withthe fastener strip with the fastener strip positioned between thevibrators.

[0066] While only a few, preferred embodiments and aspects of theinvention have been described above, those of ordinary skill in the artwill recognize that these embodiments and aspects may be modified andaltered without departing from the central spirit and scope of theinvention. Thus, the preferred embodiments and aspects described aboveare to be considered in all respects as illustrative and notrestrictive, the scope of the invention being indicated by the appendedclaims, rather than by the foregoing description, and all changes whichcome within the meaning and range of equivalency of the claims areintended to be embraced herein.

We claim:
 1. A method for sealing portions of a thermoplastic fastenerstrip, which method comprises the steps of: providing a thermoplasticfastener strip; vibrating a portion of the fastener strip so as toincrease the malleability of said portion, as compared to themalleability of the fastener strip before vibrating; pressing a firstmatrix against the malleable portion to produce a first shape; andpressing a second matrix against the malleable portion to produce asecond shape.
 2. The method of claim 1 in which the vibrating is causedby an oscillating vibrator in contact with the fastener strip.
 3. Themethod of claim 2 in which the vibrator vibrates at a frequency whichproduces a measurable increase in the temperature of the vibratedportion.
 4. The method of claim 2 in which the vibrator oscillates at afrequency of at least about 20,000 cycles per second.
 5. The method ofclaim 2 in which the vibrator includes a generally planar face having aplurality of cutouts and a groove extending from one of the cutouts toanother of the cutouts.
 6. The method of claim 2 in which the vibratoris positioned over the fastener strip and an anvil is positioned underand in contact with the fastener strip.
 7. The method of claim 6 inwhich the vibrator does not touch the anvil during the vibrating.
 8. Themethod of claim 1 in which the vibrating is caused by two or moreoscillating vibrators in contact with the fastener strip, one of thevibrators positioned over and in contact with the fastener strip and theother of the vibrators positioned under and in contact with the fastenerstrip.
 9. The method of claim 1 in which the first matrix is pressedagainst the malleable portion at a first location to produce the firstshape, the malleable portion is subsequently transferred to a secondlocation and the second matrix is pressed against the malleable portionat the second location to produce the second shape.
 10. The method ofclaim 1 in which the vibrating and the first matrix to produce the firstshape are performed at the same location.
 11. The method of claim 1 inwhich the first matrix is pressed against the malleable portion, themalleable portion is subsequently heated and the second matrix is thenpressed against the malleable portion.
 12. The method of claim 1 whichincludes heating the fastener strip to a temperature warmer than roomtemperature and cooler than the melting range of the fastener stripbefore the vibrating.
 13. The method of claim 1 which includestensioning the fastener strip and maintaining the tension during sealingof the portions of the fastener strip.
 14. The method of claim 1 whichincludes pressing a third matrix against the malleable portion toproduce a third shape.
 15. The method of claim 1 in which each of thematrices includes a die, and at least one of the dies has a generallyplanar face and a plurality of cutouts.
 16. The method of claim 15 inwhich at least one of the dies has a generally planar face and a channelextending substantially across the face.
 17. A method for making afastener strip having a permanently sealed, airtight portion adjacent areclosable portion that is essentially airtight when fastened, whichmethod comprises the steps of: providing a reclosable thermoplasticfastener strip that is essentially airtight when fastened; vibrating aportion of the fastener strip so as to increase the malleability of saidportion, as compared to the malleability of the fastener strip beforevibrating, the malleable portion being adjacent an end of a reclosableportion; pressing the malleable portion to produce a generally planarportion that is essentially airtight; displacing at least some of themalleable portion to produce an essentially airtight plug that joins theplanar portion in an essentially airtight seal, which extends from theplanar portion to the adjacent end of the reclosable portion and joinsthe adjacent end of the reclosable portion in an essentially airtightseal; and cooling the fastener strip to make a fastener strip having apermanently sealed, airtight portion adjacent a reclosable portion thatis essentially airtight when fastened.
 18. The method of claim 17 inwhich the reclosable portion includes: a) an elongated first backing,including a trough extending lengthwise along the first backing; and b)an elongated second backing, including a ridge extending lengthwisealong the second backing, the ridge removably insertable into the troughto essentially prevent air flow across the trough; and the planarportion includes essentially no ridge and essentially no trough; saidmethod including the steps of joining the ridge of the reclosableportion and the trough of the reclosable portion at the adjacent end ofthe reclosable portion so as to create the a plug in the seal thatprevents air from leaking from the adjacent end of the reclosableportion.
 19. The method of claim 18 which includes displacing at leastsome of the malleable portion to produce an essentially airtight damthat joins the plug to the first backing in an essentially airtightseal, and joins the plug to the second backing in an essentiallyairtight seal.
 20. The method of claim 17 in which displacing themalleable portion includes pressing a first matrix against the malleableportion to produce a first shape.
 21. The method of claim 20 in whichplug is formed by pressing the first matrix against the malleableportion.
 22. The method of claim 17 in which displacing the malleableportion includes pressing a second matrix against the malleable portionto produce a second shape.
 23. The method claim 22 in which the dam isformed by pressing the second matrix against the malleable portion. 24.An apparatus for sealing portions of a fastener strip, which apparatuscomprises: a vibrator for vibrating a portion of the fastener strip soas to increase the malleability of said portion, as compared to themalleability of the fastener strip before vibrating; a first matrixconstructed and arranged for pressing against the malleable portion toproduce a first shape for sealing the fastener; and a second matrixconstructed and arranged for pressing against the malleable portion toproduce a second shape for sealing the fastener.
 25. The apparatus ofclaim 24 in which the vibrator oscillates in contact with the fastenerstrip.
 26. The apparatus of claim 24 in which the vibrator is suitablefor vibrating at a frequency which produces a measurable increase in thetemperature of the vibrated portion.
 27. The apparatus of claim 24 inwhich the vibrator is suitable for oscillating at a frequency of atleast about 20,000 cycles per second.
 28. The apparatus of claim 24 inwhich the vibrator includes a generally planar face having a pluralityof cutouts and a groove extending from one of the cutouts to another ofthe cutouts so as to facilitate flow of thermoplastic material.
 29. Theapparatus of claim 24 in which the vibrator includes is positioned overthe fastener strip and an anvil is positioned under and in contact withthe fastener strip so as to facilitate sealing.
 30. The apparatus ofclaim 29 in which the vibrator does not touch the anvil during thevibrating.
 31. The apparatus of claim 24 in which the vibrator includestwo or more ultrasonic horns in contact with the fastener strip, one ofthe horns being positioned over and in contact with the fastener stripand the other of the horns being positioned under and in contact withthe fastener strip.
 32. The apparatus of claim 24 in which includes afirst stage at a first location for pressing the first matrix againstthe malleable portion, and a second stage at a second location forpressing the second matrix against the malleable portion so as toproduce the second shape.
 33. The apparatus of claim 24 in which thefirst stage is suitable for the vibrating and the malleable portionpressing so as to produce the first shape.
 34. The apparatus of claim 24which comprises a heater for pre-heating the fastener strip.
 35. Theapparatus of claim 24 and comprising a tensioner for tensioning thefastener strip.
 36. The apparatus of claim 24 which comprises a thirdmatrix for pressing against the malleable portion so as to produce athird shape.
 37. The apparatus of claim 24 in which each of the matricesincludes a die, and at least one of the dies has a generally planar faceand a plurality of cutouts.
 38. The apparatus of claim 37 in which thefirst matrix includes a die that is unitary with the vibrator.
 39. Theapparatus of claim 37 in which at least one of the dies has a generallyplanar face and a channel extending substantially across the face forpressing the fastener strip so as to form a generally planar portion andfor displacing at least some of the malleable portion beyond the planarportion so as to form an airtight seal.
 40. An apparatus for sealing aportion of a reclosable thermoplastic fastener strip that is essentiallyairtight when fastened, the fastener strip comprising: a) an elongatedfirst backing, including a trough extending lengthwise along the firstbacking; and b) an elongated second backing, including a ridge extendinglengthwise along the second backing, the ridge removably insertable intothe trough to essentially prevent air flow across the trough; theapparatus comprising: a vibrator for vibrating a portion of the fastenerstrip so as to produce a portion that is relatively more malleable, ascompared to the malleability of the fastener strip before vibrating, themalleable portion being adjacent an end of a reclosable remainderportion of the fastener strip; and at least one matrix for pressingagainst the malleable portion so as to produce a planar portion thatincludes essentially no ridge and essentially no trough and to displaceat least some of the malleable portion to form a plug which joins theridge of the reclosable portion and the trough of the reclosable portionat the adjacent end in an airtight seal that prevents air from leakingfrom the adjacent end.
 41. The apparatus of claim 40 which comprises asecond matrix for displacing at least some of the malleable portiondisplacing at least some of the malleable portion to produce anessentially airtight dam that joins the plug to the first backing of thereclosable portion in an essentially airtight seal, and joins the plugto the second backing of the reclosable portion in an essentiallyairtight seal.
 42. The apparatus of claim 40 which comprises a coolerfor cooling the fastener strip.
 43. An apparatus for vibrating a portionof a thermoplastic fastener strip, which apparatus comprises: a vibratorsuitable for oscillating at a frequency in the range of normal humanhearing or higher, the vibrator including a generally planar face havinga plurality of spaced apart cutouts; and a groove extending from one ofthe cutouts to another of the cutouts, the groove sized to receive aportion of a fastener strip including thermoplastic material and todisplace a predetermined volume of the material along the fastener stripwhen the vibrator is oscillated and pressed into the fastener strip. 44.The apparatus of claim 43 in which the groove is sized appropriately forthe vibrator to displace the volume of material when the vibrator isoscillated and pressed into the fastener strip with a predeterminedpressure.
 45. The apparatus of claim 43 in which the groove is sizedappropriately for the vibrator to displace the volume of material whenthe vibrator is oscillated and positioned at a predetermined distancefrom the fastener strip.
 46. The apparatus of claim 43 in which thecutouts are generally arcuate in section and spaced apart at apredetermined distance, each of the cutouts arching toward the other ofthe cutouts.
 47. The apparatus of claim 43 in which at least one of thecutouts includes a transition volume having a depth which increases as afunction of distance from the groove.
 48. The apparatus of claim 43 inwhich the groove has a depth which decreases as a function of distancefrom the closest of the cutouts.
 49. The apparatus of claim 43 in whichthe vibrator is suitable for pneumatically actuated oscillation atfrequencies in the range of about 10,000 to about 100,000 cycles persecond.
 50. The apparatus of claim 47 in which the fastener stripincludes an elongated first backing having a longitudinally extendingtrough; and an elongated second backing having longitudinally extendingridge, the ridge removably insertable into the trough to essentiallyprevent air flow across the trough.
 51. The apparatus of claim 50 inwhich the groove has an axis is oriented to receive the ridge and thetrough, and each of the cutouts has an axis of symmetry that isgenerally parallel and offset with respect to the groove axis.
 52. Theapparatus of claim 43 in which the vibrator is a resonator.
 53. Theapparatus of claim 43 which also includes an anvil, and the vibrator ispositioned over the anvil.
 54. A fastener strip, which comprises: areclosable portion including a) an elongated first backing, including atrough extending lengthwise along the first backing; and b) an elongatedsecond backing, including a ridge extending lengthwise along the secondbacking, the ridge removably insertable into the trough to essentiallyprevent air flow across the trough; and a generally planar portionincluding essentially no ridge and essentially no trough; and a plugthat joins the ridge of the reclosable portion and the trough of thereclosable portion at the adjacent end of the reclosable portion to theplug in an airtight seal that prevents air from leaking from theadjacent end of the reclosable portion.
 55. The fastener strip of claim54 which comprises an essentially airtight dam that joins the plug tothe first backing in an essentially airtight seal, and joins the plug tothe second backing in an essentially airtight seal.
 56. The fastenerstrip of claim 54 in which the planar portion is essentially imperviousto air flow.
 57. The fastener strip of claim 54 in which the plug isessentially impervious to air flow.
 58. The fastener strip of claim 55in which the dam is essentially impervious to air flow.
 59. The fastenerstrip of claim 54 in which the at least some of the plug is locatedbetween the ridge of the reclosable portion and the trough of thereclosable portion.
 60. A fastener strip, which comprises: a reclosableportion including a) an elongated first backing, including a troughextending lengthwise along the first backing; and b) an elongated secondbacking, including a ridge extending lengthwise along the secondbacking, the ridge removably insertable into the trough to essentiallyprevent air flow across the trough; a generally planar portion includingessentially no ridge and essentially no trough; a plug that joins theridge of the reclosable portion and the trough of the reclosable portionat the adjacent end of the reclosable portion to the plug in an airtightseal that prevents air from leaking from the adjacent end of thereclosable portion; and a dam that joins the plug to the first backingin an essentially airtight seal, and joins the plug to the secondbacking in an essentially airtight seal.